[Mp4-tech] BSAC :Separating the base layer from the enhacement layers

[akhalife uci.edu]

HI FOLKS
1)I am interested in separating the base layer of each frame from
the enhacement layers. so I wonder, is the base layer size (number of
bits) is the same for each frame?
2)Also , is the frame length is constant?(for example 20 ms ?) I mean if I
have a wav file (6 seconds), can I know how many frames do the encoder
will divide my wav file?
3)So, if the frame length is const, can I know the length of it?
I highly appreciate if you can give me hint or guide for being able to
separate the base layer from the enhacement layers. I was thinking of this
approach, since the base layer is 16 kbps,and if the frame size length is
known, for example 20 ms, so I was thinking of calculating how many bits
will go for the base layer, and how many for the enhacement layers, so by
tracing the encoded file (by looking into the bits), i can separate the
base layer of each fram. is my approach correct ?
Regards
Ala